# Sodium has an atomic number of 11 and a mass number of 23. State the number of protons, neutrons and electrons in an atom of sodium, and explain why the overall charge of a sodium atom is zero.

> Eduqas A-Level Chemistry — 2.1 Periodic table · State and Explain · 5 marks

> Sodium is an element in Group 1 of the periodic table.

## Mark scheme (5 marks)

1. Number of protons = 11
2. Number of neutrons = 12 (mass number minus atomic number: 23 − 11)
3. Number of electrons = 11
4. Protons are positively charged and electrons are negatively charged (accept: equal and opposite charges)
5. The number of protons equals the number of electrons, so the charges cancel / balance out, giving an overall charge of zero

## Key terms

- [atomic number](https://www.gradenine.co.uk/glossary/atomic-number)
- [mass number](https://www.gradenine.co.uk/glossary/mass-number)
- [proton](https://www.gradenine.co.uk/glossary/proton)
- [neutron](https://www.gradenine.co.uk/glossary/neutron)
- [electron](https://www.gradenine.co.uk/glossary/electron)

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "State and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/sodium-has-an-atomic-number-of-9b92c73e) · Published by Druglandscape Ltd.